Speed control of DC Machine
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This document discusses various methods of speed control for DC motors, including flux control and armature voltage control. It also describes different laboratory methods like the Ward Leonard method using induction, synchronous, or diesel prime movers. Types of speed control discussed include open loop and closed loop control. Static voltage control methods for AC and DC supply like converters, choppers, and PWM methods are also summarized. Preferences for different types of DC motors are stated at the end.
Speed control of DC Machine
- 1. SUBMITTED BY--VIPIN KUMAR SINGH SHAHBAAZ AHMED RAVI YADAV SHRAVAN KUMAR UNDER THE GUIDANCE OF— Mr. RANJIT KUMAR
- 2. METHODS OF SPEED CONTROL 1. FLUX CONTROL— Speed of dc motor is inversely prop. to field flux So speed can be controlled above base speed It is constant power speed control. Speed below base speed is not possible in this method.
- 3. METHODS OF SPEED CONTROL 2. ARMATURE VOLTAGE CONTROL Speed of dc machine is directly prop. to armature voltage. So speed below base speed can be controlled. It is a constant torque method. Speed reversal is possible.
- 4. LABORATORY METHOD 1. WARD LEONARD METHOD A) USING INDUCTION PRIME MOVER Induction prime mover is required with flywheel when there is heavy and intermittent load . Flywheel works as a reservoir of energy and make a flow of energy when requires.
- 5. LABORATORY METHOD B) USING SYNCHRONOUS PRIME MOVER • When P.F. improvement is requored synchronous motor is used with overexcitation. • Overexcitation of field also enhance maximum torque capability. • Application-rolling mills, elevator etc
- 6. LABORATORY METHOD C) USING DIESEL PRIME MOVER • Generater is driven by constant speed diesel engine. • Hence we have to concentrate over motor speed only • Regenerative braking is not possible.
- 7. TYPES OF SPEED CONTROL 1. OPEN LOOP SPEED CONTROL This type of control is applied when low ratings are involved. In this method simple rheostat is used as power loss in it is less at low power. Maximum speed obtained is 20*base speed. For higher rating, it is not applicable.
- 8. TYPES OF SPEED CONTROL • 2. CLOSED LOOP SPEED CONTROL • This meets the following requirements• 1)protection • 2)enhancement of speed of response • 3)to improve steady state accuracy. • Inner current control is required. • PI,PD,PID may be used as per requirement.
- 9. STATIC VOLTAGE CONTROL FOR AC SUPPLY 1. CONVERTOR A). UNCONTROLLED CONVERTOR USING TAPPED TRANSFORMER B). HALF CONTROLLED CONVERTOR C). FULL CONVERTOR
- 10. STATIC VOLTAGE CONTROL FOR AC SUPPLY 2. DUAL CONVERTOR Dual converter allows current as well as voltage in either direction. Hence 4 quadrant operation. Hence motoring and regenerative braking can be done by adjusting firing angle.
- 12. STATIC VOLTAGE FOR DC SUPPLY 1. USING CHOPPER(DC TO VARIABLE DC) IGBT,IGCT,GTO,MOSFET are used in place of scr . Important feature of chopper control is easier regenerative braking. Type A –MOTORING TYPE B-REGENERATIVE BRAKING TYPE C -BOTH
- 13. CHOPPER
- 14. PWM METHOD OF VOLTAGE CONTROL This is a supporting method, but can be used individually. It reduces the harmonics of output. In this a comparator compare the oscillator wave with square dc wave, and gives the trigger to later circuit. Later circuit may be involved of converter, chopper. This circuit gives output according to the triggered pulses. At high power level this method becomes costly.
- 15. PWM METHOD OF VOLTAGE CONTROL
- 16. PREFERENCES OF DC MOTORS 1. BRUSHLESS DC MOTORS. 2. SEPERATELY EXCITED DC MOTOR. 3. SHUNT EXCITED DC MOTOR. 4. SERIES EXCITED DC MOTOR.
- 17. REFERENCES P.S. BIMBHRA- ‘POWER ELECTRONICS’-KHANNA PUBLICATION GOPAL K. DUBEY-NAROSA PUBLISHING HOUSEII EDITION-2011 P.S. BIMBHRA-ELECTRICAL MACHINERY-KHANNA PUBLICATION